KR20040014981A - Position sensor - Google Patents

Abstract

The present invention supplies an alternating current to a detection coil from a constant current circuit, and at the same time supplies a direct current, and the variation in the temperature coefficient of the peak value of the peak value of the output voltage of the detection section of the entire displacement section is determined by the impedance of the detecting coil at the frequency of the alternating current. AC characteristics of the DC current and the alternating current ratio, the AC component and the DC component ratio of the impedance of the detection section, the temperature characteristic of the ratio of the DC current and AC current, and the impedance of the impedance of the detection section so as to be smaller than the fluctuation range of the temperature coefficient of the AC component. Any one or more of the temperature characteristic of the ratio of a component and a direct current component is set.

Description

Position sensor {POSITION SENSOR}

As a conventional position sensor, a position sensor is proposed which inserts a core into a detection coil, detects a change in impedance of the detection coil, and outputs a displacement signal. FIG. 34 is a schematic diagram of the detection unit of this position sensor, FIG. 35 is a schematic diagram showing the relationship between the core displacement X and the AC impedance Zac of the detection coil 2, and FIG. 36 is a schematic diagram of the entire circuit. In addition, the AC impedance Zac is composed of a real part and a virtual part. In FIG. 35, the larger the displacement X, the larger the amount of penetration of the core 301 into the detection coil 302, and thus the AC impedance Zac. ) Increases, but the larger the displacement X, the smaller the penetration amount of the core 301 into the detection coil 302, and the larger the displacement X, the lower the AC impedance Zac may be.

In the above conventional position sensor, in general, an alternating current is applied to the detection coil 302, the amplitude and phase of the voltage generated at both ends of the detection coil 302 are detected, and appropriate signal processing is performed. The reason why the alternating current is given here is that a voltage amplitude proportional to the alternating current impedance Zac of the detection coil 302 is obtained.

However, when the core 301 is a magnetic material, the rate of change of temperature (temperature coefficient) of the impedance Z of the detection coil 302 at the time of insertion of the core 301 is not uniform with respect to the displacement X of the core 301. Therefore, it is known that as the insertion amount of the core 301 increases as shown in FIG. 37, the temperature change rate DELTA (dZac / dt) also increases. For this reason, in order to obtain the displacement signal by temperature-compensating the output voltage of the detection coil 302, there exists a problem that a circuit structure becomes complicated.

In order to solve the above problems, there are techniques such as US Patent 5003258, US Patent 4864232, US Patent 5898300. 38 is a view described in US Patent 5003258. These are essentially detect coils to compensate for changes in temperature of impedance Z (inductance component) by magnetic material 421 of core 401 and changes in temperature of impedance Z (eddy current component) by nonmagnetic material 422. 402 is made.

That is, for the problem that the temperature coefficient of the impedance Z of the detection coil 402 depends on the displacement X of the core 401, the impedance Z is devised by devising the structure of the detection coil 402 and its surroundings. The displacement dependence of the temperature coefficient of was made small. However, even in this case, the number of parts is increased, the positioning between parts is difficult, the design constraints on the detection coil are large, the versatility is insufficient, and the problem of cost increase is caused.

Next, the relationship between the displacement X of the detection coil 302 of FIG. 34, and the alternating current impedance Zac of the detection coil 302 is shown in FIG. 35 more realistically. In FIG. 39, the linearity of the AC impedance Zac with respect to the displacement X is good with respect to the center portion of the stroke, but the linearity is worsened at both ends. In particular, the linearity is particularly bad when the penetration of the core 301 entering the detection coil 302 is small. This means that the tip portion of the core 301 has an increase in the impedance Z of the detection coil 302 compared with other portions. It is because the ratio which contributes to is low. This may be called end effect.

Usually, although a sensor is comprised so that a desired displacement section may be a section with a good linearity in a center part, there existed a problem that it was difficult to obtain desired linearity for the said reason, such as when there is a limitation in a dimension.

Next, the conventional structural problem is demonstrated. As one shape means for improving the linearity of the position sensor, the cross-sectional area of the bobbin winding portion is made as small as possible so that the ratio of the cross-sectional area of the core 301 to the cross-sectional area of the winding portion of the bobbin 315 (see FIG. 34) is increased. There is a way to make it as large as possible. In this case, the clearance between the inner wall (the side of the through hole) of the winding part of the bobbin 315 and the core 301 is preferably smaller.

Here, as long as the bobbin 315 is formed of a nonmetallic body such as plastic, even if the inner wall of the core 301 and the bobbin 315 are in contact with each other, there is no significant effect on the electrical characteristics (coil impedance, etc.), but the core 301 and the bobbin When the inner wall of 315 contacts, the core 301 and the detection coil 302 may not be relatively displaced smoothly, and may cause problems, such as deformation of the core 301 and generation of mechanical hysteresis.

In particular, in the case of the rotary position sensor, since the positioning of the curved core and the curved detection coil is difficult, the core and the inner wall of the bobbin come into contact with each other to generate the above problems.

In addition, such a rotational position sensor also has the following problems with regard to coil winding. First, since the bobbin is curved, uniform winding is difficult, and a long time is required for the winding. Moreover, when winding to a curved bobbin, the curvature of the bobbin after winding locally becomes larger than the curvature before winding due to the tension at the time of winding. As a result of the change in curvature, the inner wall of the core and the bobbin winding part is caught as described above. In an extreme case, the movable body may be displaced only to the middle.

<Start of invention>

An object of the present invention is to provide a position sensor capable of compensating a change in the temperature coefficient of the impedance of a detection coil with respect to displacement with a simple circuit.

According to an aspect of the present invention, a position sensor includes a constant current circuit for outputting a constant current superimposed on a direct current having a predetermined amplitude and an alternating current having a predetermined frequency and amplitude, a detection unit including at least a detection coil supplied with a constant current, and a detection unit. A core which is relatively displaced in the crimp direction of the detection coil relative to the coil, and a signal processing circuit which outputs a displacement signal representing the position information of the core and the detection coil based on the peak value of the output voltage of the detection portion generated by the constant current; The fluctuation range of the temperature coefficient of the peak value of the output voltage of the detector in the entire displacement section with respect to the detection coil of the core is the AC component of the impedance of the detector at the predetermined frequency in the entire displacement section with respect to the detection coil of the core. The ratio of the direct current of the constant current to the alternating current so that it becomes smaller than the fluctuation range of the temperature coefficient, and the impedance of the detection part Any of the temperature characteristic of the ratio of the scan of the AC component with the ratio of direct current component and the temperature characteristic of the constant current of the direct current and alternating current with the ratio, the impedance of the detector the AC component and the DC component is to set one or more.

According to this configuration, the detection coil can be freely selected according to the detection target, and by setting a constant on the circuit, the displacement dependency of the temperature coefficient of the impedance of the detection coil can be easily reduced, and the impedance of the detection coil with respect to the displacement can be easily reduced. Changes in the temperature coefficient can be compensated with a simple circuit.

The present invention relates to a position sensor for detecting the displacement of the moving body.

1 is a diagram showing the circuit configuration of Embodiment 1 of the present invention;

2 is a view showing an upper surface of Embodiment 1 of the present invention;

3 is a side cross-sectional view of Embodiment 1 of the present invention;

4 is a cross-sectional view of a detection coil of Embodiment 1 of the present invention;

5 is a diagram showing voltage waveforms at both ends of a detection coil according to Embodiment 1 of the present invention;

6 is a diagram showing a relationship between the rotation angle and the impedance of a detection coil according to the first embodiment of the present invention;

7 is a view showing a relationship between the rotation angle of the first embodiment of the present invention and the voltage across the detection coil;

8 is a view showing a relationship between a rotation angle of a first embodiment of the present invention and a temperature coefficient of the voltage across the detection coil;

9 is a view showing a relationship between a rotation angle of the first embodiment of the present invention and the temperature coefficient of the peak voltage at both ends of the detection coil;

10 is a diagram showing a specific circuit configuration of the constant current circuit and the signal processing circuit according to the first embodiment of the present invention;

11 is a diagram showing a specific circuit configuration of an oscillation circuit according to Embodiment 1 of the present invention;

12 is a diagram showing another circuit configuration of the voltage-current conversion circuit of Embodiment 1 of the present invention;

13 is a diagram showing another circuit configuration of the constant current circuit according to the first embodiment of the present invention;

14 is a diagram showing another circuit configuration according to the first embodiment of the present invention;

15 is a reference diagram showing a relationship between a rotation angle and a temperature coefficient of a voltage at both ends of a detection coil;

16 is a diagram showing an equivalent circuit of the detection coil of Embodiment 2 of the present invention;

17 is a view showing variation in resistance value of a copper wire due to the skin effect of Embodiment 2 of the present invention;

18 is a view showing a variation in resistance of a copper wire due to the proximity effect of Embodiment 2 of the present invention;

19 is a view showing the characteristics of the magnetic body used in the core of Embodiment 3 of the present invention;

20 is a diagram showing, for each frequency, the relationship between the linearity of the angular span and the AC impedance of the detection coil according to the third embodiment of the present invention;

21 is a view showing the ends of the core of Embodiment 3 of the present invention;

FIG. 22 is a side cross-sectional view of a position sensor in a straight stroke configuration according to a third embodiment of the present invention; FIG.

Fig. 23 is a view showing the ends of the core with the edge removed in Embodiment 3 of the present invention;

24 is a view showing a detection coil provided with holding and fixing members at both ends of Embodiment 3 of the present invention;

25 is a view showing an upper surface of a first position sensor including two detection parts according to a fourth embodiment of the present invention;

FIG. 26 is a view showing a part of side cross section of the first position sensor of Embodiment 4 of the present invention; FIG.

27 is a view showing an upper surface of a second position sensor including two detection sections according to the fourth embodiment of the present invention;

28 is a view showing a part of a side cross section of the second position sensor of Embodiment 4 of the present invention;

29 is a first diagram showing a displacement signal of Embodiment 5 of the present invention;

30 is a second diagram showing a displacement signal of Embodiment 5 of the present invention;

31 is a third diagram showing a displacement signal of Embodiment 5 of the present invention;

32 is a view showing the cross-sectional structure of Embodiment 6 of the present invention;

33 is a diagram showing the circuit configuration according to the sixth embodiment of the present invention;

34 is a side cross-sectional view of a conventional first position sensor;

35 is a view showing a relationship between a displacement of a conventional first position sensor and an alternating current impedance of a detection coil;

36 is a view showing the circuit configuration of a conventional first position sensor;

37 is a view showing a relationship between a displacement of a conventional first position sensor and a temperature coefficient of an alternating current impedance of a detection coil;

38 is a side cross-sectional view of a conventional second position sensor,

Fig. 39 is a diagram showing a relationship between a displacement of a conventional first position sensor and an alternating current impedance of a detection coil in a state close to reality.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described based on drawing.

(Embodiment 1)

The circuit structure of the position sensor of this embodiment is shown in FIG. 1, a top view is shown in FIG. 2, A-A 'sectional drawing of FIG. 2 is shown in FIG. 3, and sectional drawing of the detection coil 20 is shown in FIG.

The position sensor according to the present embodiment has a cross section U-shape, which is coated with the inside of the U-shaped coating 21 and wound around the curved bobbin 22 curved at a constant curvature, and the curved detection coil 20. The movable block 23 having the protrusion 23a formed on the outer side of the cylindrical body having the center of rotation as the rotation axis thereof, and one end thereof connected to the protrusion 23a, and curved at a constant curvature penetrating into the hollow portion of the detection coil 20. A core 60 made of a magnetic material, a curvature correction member 24 for correcting a change in curvature of the detection coil 20, a housing 25 for disposing and fixing each component on a fixed surface, and predetermined The constant current circuit 30 which outputs the constant current Id which superimposed the DC current Idc of amplitude, and the alternating current of amplitude Iac to the detection coil 20, and the constant current circuit 30, respectively. Voltage Vs at both ends of the detection coil 20 determined by the constant current Id and the impedance Z of the detection coil 20 Signal processing circuit 40 for outputting a displacement signal Vout indicating the position information of the core 60 and the detection coil 20 in accordance with the peak value V1 of the signal), and the detection coil 20 The detector 50 is supplied with a constant current Id and outputs a detection signal. In addition, in this embodiment, although the cross-sectional shape of the curved bobbin 22 was formed in the U shape which is easy to form by injection molding etc., another shape may be sufficient.

Then, as the movable block 23 rotates and the rotation angle θ becomes from 0 ° to 90 °, a portion of the core 60 penetrated into the detection coil 20 is reduced. In addition, the constant current circuit 30 includes an oscillation circuit 30a for generating a constant voltage Vd 'obtained by superimposing an alternating voltage of a predetermined frequency f and an amplitude Vac' on a DC voltage Vdc 'having a predetermined amplitude; It consists of the voltage-current conversion circuit 30b which converts the constant voltage Vd 'which the oscillation circuit 30a outputs into the constant current Id.

First, the temperature characteristic of the detection signal of the detection part 50 is demonstrated based on a specific example. In a normal position sensor, an output linearity error of a detection signal in a predetermined displacement section is defined at room temperature, and a constant margin is given thereto to define a value in the entire operating temperature range. For example, "An angular range θ = 0 to 90 ° of position detection, and the linearity error of the detection signal is ± 1% FS or less at room temperature, ± 2% FS or less at -40 to + 130 ° C ''. . In this case, the deterioration of the linearity error due to the temperature fluctuation factor should be suppressed to about ± 1% FS. If the room temperature is 30 ° C, since the high temperature side has a temperature range of 100 ° C, if the detection signal assumes a linear change with temperature, the fluctuation range of the temperature change rate (temperature coefficient) should be suppressed to ± 100 ppm / K or less. .

Moreover, also in the arbitrary change in a desired displacement range, if the fluctuation range (DELTA) (dV1 / dT) of the temperature coefficient of the peak value V1 of the voltage Vs of both ends of the detection coil 20 is ± 100 ppm / K or less, By adding a simple temperature compensation circuit with a constant temperature coefficient, the voltage after temperature compensation can be set to the normal temperature value ± 100 ppm / K at the displacement. This is the orientation of the present embodiment.

Next, the operation of the present embodiment will be described. As shown in FIG. 1, the alternating current Iac is supplied from the constant current circuit 30 to the detection coil 20, and the direct current Idc is supplied. When the DC resistance of the detection coil 20 is Zdc and the AC impedance at the oscillation frequency f of the AC current Iac is Zdc and the voltage at both ends of the detection coil 20 is Vs, the voltage Vs is the DC voltage ( Is thought to be the sum of Vdc) and the alternating voltage (Vac),

Vs = Vdc + Vac = Idc × Zdc + Iac × Zac

It can be represented as. In Equation 1, all quantities are complex numbers, but considering only the peak voltage V1 of the voltage Vs,

V1 = Vdc + Vac = Idc × Zdc + Iac × Zac

All quantities in Equation 2 can be treated as real numbers, and the waveform is the sum of the DC voltage Vdc and the AC voltage Vac having the peak voltage V1, as shown in FIG. have.

FIG. 6 is sample data created based on actual values of impedances of the detection coil 20 wound with a copper nickel alloy wire (GCN15 wire), and illustrates a direct current resistance Zdc and an alternating current impedance Zac of the detection coil 20. It is plotted on the graph which made the rotation angle (theta) of 2 the horizontal axis. Here, although the impedance Z is set so that it may change completely linearly with respect to the rotation angle (theta), it becomes a value considerably close to actual value. Moreover, each data in ambient temperature: -40 degreeC, +25 degreeC, +85 degreeC, and +130 degreeC is shown.

And at an ambient temperature of + 25 ° C, the DC resistance Zdc is 188 Ω, the temperature coefficient is 511 ppm / K, and the AC impedance Zac is

Zac = (Z0 + Z '× θ) × {1 + (β0 + β' × θ) × T}

Z0 = 636Ω, Z '= -3.48Ω / deg, β0 = 478ppm / K, β' = -2.49ppm / K / deg, θ is a rotation angle, and T represents a celsius temperature. Here, the temperature coefficient of the AC impedance Zac is 478 ppm / K at θ = 0 °, and 254 ppm / K at θ = 90 °, so the fluctuation range Δ (dZac / dT) reaches 224 ppm / K.

Next, the DC current Idc = 1.5 mA and the AC current Iac = 0.3 mA output from the constant current circuit 30 are set. For simplicity, the temperature change rate of the DC current Idc, the AC current Iac, and the frequency f is determined. The result of plotting DC voltage (Vdc), alternating voltage (Vac), and peak voltage (V1) at both ends of the detection coil 20 at zero as shown in Equation 2 is shown in FIG. Each plot, and their temperature coefficient is FIG.

As can be seen from FIG. 8, over a rotation angle θ = 0 ° to 90 °, the temperature coefficient of the peak voltage V1 is approximately 450 to 500 ppm / K, and the fluctuation range Δ (dV1 / dT) is approximately 50 ppm /. K, very narrow fluctuations. Therefore, when temperature compensation of about 470 ppm / K is performed to peak voltage V1, the voltage after compensation can be returned to a normal temperature value with almost no error.

Next, with the alternating current Iac outputted by the constant current circuit 30 = 0.3 mA, the temperature coefficient of the peak voltage V1 when the DC current Idc is changed is calculated in the same manner as in FIG. 8. 9. If the direct current Idc = 0, the displacement dependency of the temperature coefficient becomes equal to the displacement dependency of the impedance Z of the detection coil 20. However, as the DC current Idc increases, the temperature coefficient of the DC voltage Vdc approaches. The smaller the amount of penetration of the core 60 into the detection coil 20 (in the present embodiment, the larger the rotation angle θ is in the region), the more the ratio of the DC voltage Vdc occupies the peak voltage V1. Since it is large (refer FIG. 7), it is easy to be influenced by the DC voltage Vdc.

When the DC current Idc is mixed even a little, the fluctuation range Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1 is considerably improved than when the DC current Idc = 0, and the DC current ( As Idc is increased, the fluctuation range Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1 becomes smaller, but the degree of improvement is saturated at any level. Therefore, increasing the DC current Idc may lead to an increase in the consumption current, so that the DC current from the allowable current consumption and the value of the fluctuation range? (DV1 / dT) of the temperature coefficient of the peak voltage V1. What is necessary is just to select the appropriate value of (Idc). At this time, by setting the DC voltage Vdc 'and the AC voltage Vac' generated by the oscillation circuit 30a, the ratio of the DC current Idc and the AC current Iac of the constant current Id can be set. have.

Further, as the frequency f of the AC voltage Vac 'generated by the oscillation circuit 30a is higher, the ratio of the AC voltage Vac to the DC voltage Vdc increases, so that the frequency f is appropriately adjusted. By selecting, the ratio of Vdc and Vac can be set appropriately, and the same logic as above is established.

In the above description, the temperature change rates of the direct current (Idc), the alternating current (Iac), and the frequency (f) are set to zero. However, when these have temperature coefficients, the direct current voltage (Vdc) and the alternating voltage ( Each temperature coefficient of Vac) shifts up and down, and the temperature characteristic of the peak voltage V1 also changes accordingly.

8 and 9, (dV1 / dT) is greatly influenced by (dVdc / dT) when the penetration amount of the core 60 is small, and when the insertion amount of the core 60 is large, dVac / dT) is greatly affected. This is naturally true from the composition ratio of the direct current voltage Vdc and the alternating voltage Vac to occupy the peak voltage V1. Regardless of the penetration amount of the core 60, the value of (dV1 / dT) is between the value of (dVdc / dT) and the value of (dVac / dT).

In addition, when the value of (dVdc / dT) and the value of (dVac / dT) in the case where the amount of penetration of the core 60 is large (near rotation angle θ = 0 °) are set to be as close as possible, (dV1 / dT) also penetrates the core 60 even when the penetration amount of the core 60 is large (it is easily affected by the temperature coefficient of the alternating voltage Vac, but the DC voltage Vdc and the AC voltage Vac are close). Even when the amount is small (preferably affected by the temperature coefficient of the original DC voltage Vdc), the value is close to (dVdc / dT), and the fluctuation range Δ (dV1 / dT) of the temperature coefficient of the peak voltage V1 It is easy to make small.

Furthermore, the value of (dVdc / dT) is close to the value of (dVac / dT) when the penetration amount of the core 60 is the minimum, and the value of (dVac / dT) when the penetration amount of the core 60 is the maximum. In the case where it is close, it can be said that the latter side can make small the fluctuation range (DV1 / dT) of the temperature coefficient of the peak voltage V1.

Specifically, by the method described later, the temperature coefficients of the DC resistance (Zdc), AC impedance (Zac), DC current (Idc), AC current (Iac), and frequency (f) are set to appropriate values, and (dVdc). / dT) or (dVac / dT).

First, the temperature coefficient of the direct current resistance Zdc is determined by the selection of the winding material of the detection coil 20. As the winding material, nichrome wires, manganese wires, and copper nickel alloy wires (GCN wires) are also practical in addition to ordinary copper wires. Although a normal copper wire has a large temperature coefficient of volume resistivity, it is characterized by a small value of volume resistivity, and the above-mentioned other wires have a feature of large volume resistivity but a small temperature coefficient. In the case of a copper nickel alloy wire, the volume resistivity and its temperature coefficient can be selected according to the alloy ratio of copper and nickel.

Next, a method for providing a suitable temperature coefficient to the direct current (Idc), alternating current (Iac), and frequency (f) will be described. As shown in FIG. 10, the constant current circuit 30 includes an oscillation circuit 30a and a voltage-current conversion circuit 30b that output a voltage of Vdc '± Vac', and the voltage-current conversion circuit 30b includes: A resistor R11 having one end connected to the control power supply Vcc, an emitter connected to the other end of the resistor R11, a base connected to the oscillation circuit 30a, and a collector connected to the detection coil 20. It consists of a PNP type transistor Q11. The signal processing circuit 40 uses a peak hold rectifier circuit as a specific circuit for extracting the peak voltage V1. The circuit includes a constant current source I1 having one end connected to the control power supply Vcc, and a constant current source. The collector is connected to the other end of (I1), the base-collector is connected, the collector is connected to the NPN transistor Q12 having the emitter connected to the detection coil 20, and the control power supply Vcc, NPN transistor Q13 having a base connected to the base of Q12, a capacitor C11 connected between an emitter and a gland of transistor Q13, and a parallel circuit of constant current source I2. The voltage at both ends of C11 is a voltage obtained by rectifying and holding the voltage Vs at both ends of the detection coil 20, that is, the peak voltage V1, and is output as the displacement signal Vout.

As shown in Fig. 11, the oscillator 30a outputting a Vdc '± Vac' voltage includes a resistor R13 connected between the comparator CP11 and the non-inverting input terminal and the output terminal of the comparator CP11. A DC power supply E11 connected between the inverting input terminal of the comparator CP11 and the ground to output the voltage Vcc / 2, a resistor R14 having one end connected to the output terminal of the comparator CP11, The other end of the resistor R14 is connected to the inverting input terminal and the DC amplifier E11 is connected to the non-inverting input terminal. The operational amplifier OP1 is connected between the inverting input terminal and the output terminal of the operational amplifier OP1. Between the capacitor R12 and the resistor R12 connected between the output terminal of the operational amplifier OP1 and the non-inverting input terminal of the comparator CP11, between the output terminal of the operational amplifier OP1 and the control power supply Vcc. It consists of a series circuit of connected resistors R15 and R16.

In this circuit, the output Vosc of the operational amplifier OP1 becomes a triangular wave with Vcc / 2 as the offset center, and divides the output Vosc by the resistors R15 and R16, so that the DC voltage Vdc 'and the AC voltage (Vac ') is determined. Such a triangular wave oscillation circuit can realize a circuit which is stable against a temperature change with a simple structure compared with a sine wave oscillation circuit. Even a square wave oscillation circuit can form a stable circuit at low cost, but even if a square wave current is applied to the detection coil 20, since only a signal voltage that is difficult to control due to di / dt of the square wave current is generated, it can be used. none. In this respect, the output voltage reflecting the rotation angle θ of the core can be obtained similarly to the triangular pie surface sine wave.

In Fig. 11, the oscillation frequency f of the AC voltage Vac 'is proportional to (R13 / (C12 x R14 x R12)), and the amplitude is proportional to (R12 / R13). Therefore, the value and temperature coefficient of the direct current voltage Vdc 'or the alternating voltage Vac' can be controlled by appropriately selecting the values and the temperature coefficients of the resistors R12 to R16 and the capacitor C12. In particular, even when the entire constant current circuit 30 becomes a monolithic IC, since the capacitor C12 is often attached to the outside, a method of adjusting the temperature coefficient with the capacitor C12 is effective.

In addition, when the whole constant current circuit 30 is monolithic IC, the resistance value of one part or all part of resistors R12-R16 is set by digital trimming, DC current Idc, alternating current Iac, and An appropriate temperature coefficient may be given to the frequency f. In this case, even if the core 60, the detection coil 20, and the displacement interval thereof are changed, the IC can be used without changing the IC, thereby increasing the versatility.

Here, digital trimming refers to connecting a parallel circuit of a resistor and a switch element in parallel with a resistor to be adjusted in advance, and performing resistance adjustment by turning the switch element on and off with digital data. Specifically, in the case of digital trimming, the optimum code of the digital data is determined while monitoring the electrical characteristics, the determined optimal code is written in the ROM of the IC, or the fuse is burned for the data storage installed in the IC. By giving a code, the resistance in the IC is set to a value corresponding to this optimum code.

In addition, the triangle wave generating circuit may not be the circuit structure shown in FIG. 11, but may be another circuit structure. In the voltage-current conversion circuit 30b of FIG. 10, the DC voltage Vdc 'generated by the oscillation circuit 30a is generated by the temperature characteristic of the base-emitter voltage Vbe of the transistor Q11. Even if the temperature coefficient of) is zero, the direct current (Idc) supplied to the detection coil 20 has a positive temperature coefficient.

If the temperature coefficient of the DC current Idc is not desired to be a positive temperature coefficient, the emitter of the transistor Q11 of the voltage-current conversion circuit 30b shown in FIG. 10 is connected to the inverting input terminal. An oscillation circuit is provided at the non-inverting input terminal of the operational amplifier OP2 by using the voltage-current conversion circuit 30b 'shown in FIG. 12 to which the operational amplifier OP2 connecting the base of the transistor Q11 to the output terminal is added. What is necessary is just to connect the output of 30a.

FIG. 13 is a circuit configuration of a constant current circuit 30 'different from the constant current circuit 30 of FIG. 10, and the constant current circuit 30' is composed of an alternating current supply circuit Sac and a direct current supply circuit Sdc. . The AC current supply circuit Sac includes a series circuit of the NPN transistor Q14 and the PNP transistor Q16, an AC signal source AC connected to the connection center of the transistors Q14 and Q16, and a control power supply Vcc. Connected to the series circuit of the PNP transistor Q18, NPN transistor Q15, PNP transistor Q17, and NPN transistor Q20 connected between -Vee and transistors Q15 and Q17. It consists of a series circuit of one resistor (R17), a PNP transistor (Q19) and an NPN transistor (Q21), and each gate of transistors Q14, Q15, transistors Q16, Q17, transistors Q18, Q19, transistors Q20, Q21 They are interconnected, and the emitters of transistors Q14, Q16, transistors Q15, Q17 are interconnected, and the base collectors of transistors Q14, Q16, Q18, Q20 are short-circuited.

In this configuration, the transistors Q14, Q15, Q16, and Q17 are part of the output circuit of a general operational amplifier circuit, the AC signal source AC is its input, and the resistor R17 can be regarded as a load resistor. The current flowing to the load through the output transistors Q15 and Q17 is copied to the current mirror made up of the transistors Q18, Q19, transistors Q20 and Q21 and applied to the detection coil 20. In this case, desired temperature characteristics can be set for the alternating current Iac by having the temperature coefficient appropriate for the amplitude, frequency, and resistance R17 of the alternating current signal source AC.

The DC current supply circuit Sdc is connected between a collector and a ground of the PNP type transistors Q22 and Q23 in which a collector is connected to the connection point of transistors Q19 and Q21, and an emitter is connected to a control power supply (Vcc). Comprising a resistor R18, the gates of the transistors Q22 and Q23 are interconnected, and the base-collector of the transistor Q23 is shorted.

In this example, a circuit for providing a positive DC current is used. However, when it is appropriate to provide a negative DC current according to the coil specification or frequency, the polarities of the transistors Q22 and Q23 are NPN type, and these emitters are controlled. Connect to the power supply (Vee). In this case, desired temperature characteristics can be set for the direct current Idc by giving the resistor R18 an appropriate temperature coefficient. In addition, by connecting one end of the resistor R18 to a predetermined potential instead of a ground, and having an appropriate temperature coefficient at the potential, a desired temperature characteristic can be set in the direct current Idc.

One end of the detection coil 20 is connected to the connection centers of the transistors Q19 and Q20, and the AC current supply circuit Sac for supplying the AC current Iac and the DC current supply circuit Sdc for supplying the DC current Idc. ) Exist independently, so that the ratio of the alternating current Iac and the direct current current Idc and the temperature coefficient can be controlled easily, and setting by digital trimming is also possible.

In addition, the signal processing circuit 40 includes an amplifier having a temperature coefficient of reverse polarity with the temperature coefficient of the peak value V1 of the output voltage of the detector 50, and based on the output of this amplifier, the displacement signal Vout ), The output of the amplifier is a signal that depends on the displacement of the temperature compensation completion, and by processing this output, a displacement signal of the temperature compensation completion can be obtained.

Next, not only the constant current circuit 30 is adjusted, but also the values of the DC resistance Zdc and the AC impedance Zac and the temperature coefficient can be controlled. Instead of the detection unit 50 described in the description of FIG. 1, as shown in FIG. 14, a detection unit including a circuit element 51 having a DC resistance Zdc 'and an alternating impedance Zac' in series with the detection coil 20. (50a) is used. At this time, the DC resistance Zdc 'and the AC impedance Zac' of the circuit element 51 are not related to the rotation angle θ of the core 60, and the DC resistance Zdc 'and the AC impedance Zac' If appropriately selected, the temperature value and the temperature coefficient of the voltage between both ends of the detector 50a can be controlled.

For example, when the circuit element 51 is a forward resistance, it becomes AC impedance Zac '= R (resistance value). If the circuit element 51 is an inductance, both the DC resistance Zdc 'and the AC impedance Zac' are provided. In addition, when a diode is provided as the circuit element 51, it can influence as much as the direct current component Vdc of the voltage Vs of both ends of the detection coil 20.

As described above, by providing not only the alternating current Iac but also the direct current (Idc) to the detection coil 20, the variation range Δ of the temperature coefficient of the signal voltage in the displacement section (rotation angle θ) Although (dV1 / dT) can be made considerably small, it is clear that the smaller Δ (dZac / dT) can also decrease Δ (dV1 / dT). The US patent described in the prior art is a technology consistent with this purpose, but has a problem as described above.

Moreover, in order to make (DZac / dT) small, it is preferable that the core 60 is a magnetic substance with a small temperature coefficient of permeability and resistivity. Since the magnetic coefficient of the magnetic permeability is not so large in the temperature range of about -40 to + 130 ° C, for example, a material having a small temperature coefficient of resistivity is particularly suitable. Nichrome (nickel, chromium, iron alloys) or iron chromium (iron, chromium, aluminum alloys) are examples. These metal materials are widely used for heating wire applications, and can be obtained very cheaply as wire rods. Therefore, when the core 60 is formed by bending the wire rod, the core 60 having excellent temperature characteristics can be manufactured at low cost, which will be described in detail in the second embodiment.

Next, although different from the gist of the present invention, if the setting of the direct current (Idc), the alternating current (Iac), the direct current resistance (Zdc), the alternating current resistance (Zac) and their respective temperature coefficients is not appropriate, Δ (dV1 / dT) Will be described as an example where?) Can be larger than Δ (dZac / dT). For example, as the detection coil 20, the DC resistance (Zdc = 100 Ω) (temperature coefficient 50 ppm / K) and the AC impedance Zac are represented by Equation (3), where Z0 = 800 Ω and Z '= -8 Ω / deg. , β0 = 346ppm / K, β '=-2.35ppm / K / deg, and the DC current (Idc = 0.2mA) and the alternating current (Iac = 1.0mA) (the temperature coefficient (0)) A plot corresponding to FIG. 8 in the case is FIG. 15. It can be seen that Δ (dV1 / dT) is larger than Δ (dZac / dT). As described above, it is emphasized that simply applying the DC current Idc does not reduce Δ (dV1 / dT).

In addition, in this embodiment, although it demonstrated with the rotation type position sensor, the same effect can be acquired even if it uses the position sensor of a straight line in the displacement direction as shown in the prior art example of FIG.

(Embodiment 2)

In the present embodiment, the temperature change of the impedance Z of the detection coil 20 does not change due to the relative displacement of the core 60 and the detection coil 20 as Δ (dZac / dT) is a minimum or more state. The method of temperature compensation is demonstrated. The structure of the position sensor of this embodiment is the same as that of Embodiment 1, the same code | symbol is attached | subjected to the same structure, and description is abbreviate | omitted.

First, as a first method of temperature compensation, the temperature when the core 60 penetrates into the detection coil 20 the rate of change of the impedance Z when the core 60 does not penetrate the detection coil 20. The method of adjusting to the rate of change will be described.

The impedance Z of the detection coil 20 is equivalent to the series circuit of the resistance component Rs and the inductance component Ls, as shown in FIG. The inductance component (Ls) has a component due to the skin effect, and the skin effect when the skin thickness is thin enough and the frequency is constant is proportional to 1/2 of the volume resistivity (ρ), so the temperature coefficient is also the volume resistivity (ρ). Is affected by the power of 1/2. Fig. 17 is a graph showing the change in the resistance value of the copper wire due to the skin effect, and shows the relationship between the frequency and the resistance value of the copper wire. The curves (Y7, Y8, Y9, Y10) correspond to the line diameters of 0.32 mm, 0.16 mm, 0.10 mm, and 0.07 mm, respectively, and the change of resistance due to the coil diameter and frequency of the coil under the influence of the skin effect. This changes.

The temperature coefficient of the resistance component Rs largely depends on the temperature coefficient of the volume resistivity p of the winding material, and the resistance component Rs is also affected by the proximity effect. Fig. 18 is a graph showing the change in the resistance value of the copper wire due to the proximity effect, and shows the relationship between the frequency and the resistance value of the copper wire. The curves Y11 and Y12 correspond to 0.16 mm and 40T, 0.07mm, and 60T of the linear diameters and the number of windings, respectively. The proximity effect is a phenomenon in which a current does not flow uniformly in the winding when the winding pitch of the coil is narrow. The narrower the winding pitch, the stronger the effect, but the influence also varies depending on the wire diameter. Since the component due to the proximity effect depends on the −1 power of the volume resistivity p, the temperature coefficient is also affected by the −1 power of the volume resistivity p.

That is, when the linear diameter is thick or the frequency is high, the temperature coefficient of the impedance Z when the core 60 does not penetrate is reduced by the skin effect and the proximity effect. Therefore, by appropriately setting the volume resistivity (rho), the wire diameter, the number of windings, the winding pitch, and the frequency of the winding material, the DC resistance component, the skin effect component, and the proximity effect in the displacement state where the core 60 does not penetrate. Since the balance of components can be controlled and the temperature coefficient of the impedance Z of the detection coil 20 can be reduced, the conventional problem of changing the temperature coefficient by the displacement amount can be solved.

Since copper has a very large temperature coefficient of volume resistivity p, it is preferable to select a winding material having a smaller temperature coefficient of volume resistivity p than copper. Specifically, the winding of the detection coil 20 may be formed of any one of nichrome, manganine, and copper-nickel alloy. In particular, a copper-nickel alloy is suitable because the value of the volume resistivity ρ can be controlled by changing its component ratio.

Next, the temperature compensation rate of the temperature change rate of the impedance Z when the core 60 penetrates into the detection coil 20 is matched to the temperature change rate when the core 60 does not penetrate the detection coil 20. The second method will be described.

As the core 60 penetrates into the detection coil 20, the increase in the impedance Z of the detection coil 20 is caused by the volume resistivity p and the permeability μ of the core 60. Therefore, since the temperature coefficient also relates to the temperature coefficients of the volume resistivity ρ and the magnetic permeability μ of the core 60, the temperature coefficient when the core 60 penetrates into the detection coil 20 is determined by the core ( The core 60 having a suitable volume resistivity p and a permeability mu is selected to match the temperature coefficient when the 60 is not intruding into the detection coil 20. Alternatively, the surface treatment of the surface of the core 60 with suitable volume resistivity p and permeability mu may be performed.

Generally, the atmospheric temperature using a position sensor is 120-130 degreeC at most, and the Curie temperature of the core 60 is sufficiently higher than the atmospheric temperature. The magnetic permeability mu has a characteristic of rapidly decreasing near the Curie temperature, and conversely, the magnetic permeability mu almost does not change in the temperature region using the position sensor.

Therefore, by using the core 60 having at least its surface formed of a material having a small change in the volume resistivity ρ which is another factor due to the increase in the impedance Z of the detection coil 20, the impedance Z Can be made small, and the fluctuation | variation by the temperature of the impedance Z of the detection coil 20 can be made small.

For example, in the position sensor which performs position detection by the impedance change of the detection coil 20 of Embodiment 1, most of the details of this impedance are inductance, and the magnetic field which arises from the constant current flowing through the detection coil 20 is detected. It becomes the axial direction of the coil 20. Then, an annular current (that is, an eddy current) that tries to eliminate this axial magnetic field flows inside the core 60. This annular current has the effect of lowering the inductance of the detection coil 20, and the magnitude is related to the volume resistivity of the core 60, in addition to the magnitude and frequency of the applied magnetic field (which does not change if it is a constant current or a fixed frequency). . That is, the larger the volume resistivity of the core 60, the smaller the annular current is, and the lower the inductance. Therefore, if the volume resistivity of the core 60 has a temperature characteristic, the temperature characteristic also occurs in the inductance, and the temperature characteristic of the inductance greatly affects the temperature characteristic of the impedance.

In practice, when the detection coil 20 is used as an impedance element, the current supplied to the detection coil 20 is often driven from several tens of power to several hundreds of power. Therefore, the magnetic field generated by the detection coil 20 at the frequency is a core. It does not reach inside of (1), but collects in the vicinity of a surface.

Therefore, the material may be formed on at least the surface of the core 60 using any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, an iron-nickel alloy, and manganine, which has a small volume resistivity (ρ). . Since these materials are called heat transfer materials, the temperature coefficient of resistance is small, and iron and nickel are magnetic materials, so they are magnetic as alloys, and therefore, the impedance change of the detection coil 20 can be largely taken.

However, not only the surface but also the core 60 with a small volume resistivity formed in bulk shape can have more excellent temperature characteristics. In this case, a heat transfer material such as a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and manganese is used, and they form a shape of the core 60 by punching from a flat plate. It is expensive to obtain a lot of material loss.

Therefore, since these materials are on the market as heating wires, heating wires made of nickel-chromium alloys, nickel-chromium-iron alloys, iron-chromium-aluminum alloys, copper-nickel alloys, manganese, and the like are cut into required sizes. By performing necessary bending processing (or stretching processing), it is possible to prevent the generation of economical and useless industrial waste.

Moreover, temperature compensation can be performed effectively by combining both the 1st method and the 2nd method of temperature compensation of this embodiment.

(Embodiment 3)

In this embodiment, improvement of the linearity of an output is demonstrated. The structure of the position sensor of this embodiment is the same as that of Embodiment 1 or 2, the same code | symbol is attached | subjected to the same structure, and description is abbreviate | omitted.

First, as a first method of improving linearity, one suitable for the material of the core 60 is selected, and the frequency f of the alternating current Iac is also appropriately set. The inventor of this invention performed the experiment regarding the linearity of alternating current impedance Zac in the detection coil 20 mentioned in Embodiment 1 by changing a core material. Fig. 19 shows used metal materials: electronic soft iron, permalloy, electronic stainless steel, SUS430, iron chromium, and their estimated characteristic values: resistivity. In FIG. 19, the term "electromagnetic stainless" is used as a metal containing Si, Mn, P, Ni, Ti, etc. in addition to 11% Cr, and is used for solenoid valves, relay yokes, and the like. Moreover, in order that each metal may extract each magnetic characteristic, heat processing is performed on the conditions inherent to each metal, and the shape is the same.

Experimental results of linearity of the AC impedance Zac of each metal with respect to the frequency f of the alternating current Iac in FIGS. 20A to 20E for 10 Hz, 30 Hz, 50 Hz, 70 Hz, and 90 Hz Shows. It can be seen that magnetic stainless steel (electromagnetic stainless) has good linearity as compared to electronic soft iron and pure iron. In particular, SUS430 (18Cr ferritic stainless steel) is suitable as a core material of the position sensor because it has good linearity with respect to angular span and also has corrosion resistance and is inexpensive. These linearities are considered to be determined by the balance of resistivity, permeability, and frequency characteristics. Since iron chromium also has good linearity at 50 kPa or more, it can be seen that, by taking countermeasures against corrosion resistance, a good core material can be obtained in combination with the advantages of the temperature change rate of the resistivity described above.

As a 2nd improvement method, the countermeasure for reducing the edge effect mentioned as a problem of the prior art is taken. 21 (a) and 21 (b) are methods for increasing the contribution rate to the AC impedance Zac of the core tip portion 60a or 60b by devising the shape of the core 60. In FIG. 21 (a), the tip portion 60a is thickened by providing a substantially perpendicular step. In FIG. 21 (b), the tip portion 60b is thickened in a wedge shape, and both of the tip portions 60a or 60b are formed. Since it is thicker than other parts, the amount of link magnetic flux between the windings can be increased, which can contribute to an increase in inductance. In addition, in the case of forming the core 60 by etching or metal injection molding, there is no particular cause of cost increase.

21C shows that by configuring the tip portion 60c of the core 60 with a material having a higher permeability than the core body, the amount of link magnetic flux at the core tip portion 60c can be increased, thereby contributing to an increase in inductance. It is. 21 (a) and 21 (b) have to be thinned at portions other than the tip portion, and accompanied with a slight decrease in sensitivity, while the decrease in sensitivity does not occur in the example of FIG. 21 (c). Moreover, since thickness is uniform, it is dynamically stable (it hardly deforms even if it hits a little).

Fig. 21 (d) shows an example of surface treatment (plating or the like) on the core tip portion 60d with a material having a high permeability. It can improve that FIG.21 (c) is cumbersome in manufacture, and difficult to position. In addition to the plating, for example, a constitution such as attaching a thin film having a high permeability may be used.

The position sensor shown in FIG. 22 displaces the detection coil 20 'wound around the hollow bobbin 15, and the detection coil 20' in the winding axial direction X, and penetrates into the hollow part of the bobbin 15. FIG. The core 61 is provided, and the constant current circuit and the signal processing circuit (not shown) are provided in the same manner as in the first embodiment. This example is an example in which the core 61 has a conventional shape and a winding is wound thickly (that is, a large number of turns) at the end of the detection coil 20 '. Therefore, also in the penetration of only the front end of the core 61, since the magnetic flux of many windings is linked, inductance increases more.

In addition, in order to prevent the core 61 and the detection coil 20 'from engaging with the bobbin inner wall, in the example of FIGS. 23A to 23E, edges such as chamfering and R are attached to the tip of the core 61. By introducing the removal structure, the jam is eliminated. In the example of FIGS. 23 (b) to 23 (e), chamfering and R attachment are performed at the tip of each core as shown in FIGS. 21 (a) to 21 (e).

In addition, in FIG. 4 which shows sectional drawing of the core 60 and the detection coil 20, the coating 21 which deposited nonmagnetic metal, such as copper, on the inner surface of the curved bobbin 22 which the core 60 penetrates is shown in FIG. To remove the jammed core 60. In the case of using a conductive material such as a metal as the coating 21, it is necessary to prevent the material from forming a closed loop in the cross section. Instead of metal deposition or the like, a part of the through hole side surface may be formed of a sheet metal part, and the same effect can be obtained as long as it is a material having slide mobility and wear resistance such as fluorine coating. In this way, the core 60 can be displaced along the side surface of the through-hole of the curved bobbin 22 by using a thin body or a linear state body (particularly amorphous, etc.), thereby achieving thinness and miniaturization and improving linearity. Also effective.

In addition, when the winding of the detection coil 20 is formed using the spring coil, and the spring coil is inserted into the curved bobbin 22, the winding having a uniform pitch in the angular direction can be easily formed.

Next, in FIG. 2, the curvature correction member 24 for transforming the winding bobbin of the detection coil 20 and returning the curved bobbin which the curvature increased to the original form is provided, and the curvature correction member 24 is provided. ) Forms a groove formed with a curvature substantially the same as that of the detection coil 20, and by inserting the detection coil 20 into the groove, the inner radius portion and the bottom surface side of the detection coil 20 have a curvature correction member 24. ), The increase in the curvature of the curved bobbin 22 is corrected. In FIG. 2, although the housing 25 is equipped with the curvature correction member 24, you may form the same groove | channel in the housing 25 itself.

The structure using such a curvature correction member 24 has a merit also in another meaning. In the detection coil which does not take such a structure, as shown in FIG. 24, it is necessary to provide the holding / fixing member 26 for holding | maintenance fixing to the outer side of the awning of both ends of the detection coil 20. As shown in FIG. If this holding / fixing member 26 is present, the stroke (mechanical displacement amount) of the core 60 is limited. However, in the case of Fig. 2 in which the structure of the holding fixing is not on the outside of the sunshade, the stroke of the core 60 can be made long, or instead of making the stroke long, the angle of the winding portion of the curved bobbin 22 can be made wide. Can also lead to an improvement in linearity.

(Embodiment 4)

The position sensor of this embodiment shown to FIGS. 25-28 is shown to FIG. 2, FIG. 3 based on the idea of a fail-safe system in consideration of using for the automobile (for example, detection of an accelerator pedal position, etc.). The detection unit of the position sensor is doubled, and the two detection coils 20a are rotated about two detection coils 20a and 20b curved at the same curvature and the rotation axis of the movable block 23A in FIGS. 25 and 26. And two cores 60a and 60b curved at the same curvature to be respectively penetrated into 20b, and the two detection coils 20a and 20b are disposed so as to overlap in the rotation axis direction of the cores 60a and 60b. Compared with the structure of arrange | positioning two detection coils on the same plane as described in Unexamined-Japanese-Patent No. 2000-186903, the anticipated angle of the winding part of detection coil 20a, 20b and the mechanical rotation angle of movable block 23A also increase. . Therefore, the range of the rotation angle (theta) with favorable linearity of each impedance Z of detection coil 20a, 20b becomes wide. In addition, since the specifications of the detection coils 20a and 20b are the same, the characteristics of the two detection coils 20a and 20b can be made substantially the same, which is advantageous in terms of winding processing and cost.

In addition, the position sensor shown in FIG. 27, FIG. 28 is the detection coil 20c curved by the large curvature (small curvature radius), the detection coil 20d curved by the small curvature (large curvature radius), and the movable block ( A core 60c curved with a large curvature penetrating into two detection coils 20c 20d by rotating about the rotation axis of 23B, and a core 60d curved with a small curvature are provided. 20d) is arrange | positioned on the same rotation angle (theta), and on the same plane with respect to the rotation axis of core 60c, 60d. Therefore, similarly to the position sensors shown in Figs. 25 and 26, the expected angles of the windings of the detection coils 20c and 20d and the mechanical rotation angles of the movable block 23B also increase, so that the detection coils 20c and 20d The range of the rotation angle (theta) with favorable linearity of each impedance Z becomes wider, and also thinning is attained.

Here, after winding the detection coil 20a, 20b (20c, 20d) of this embodiment to the curved bobbin 22a, 22b (22c, 22d), and before assembling, it detects the detection coil 20a, 20b (20c). 20d) and the curved bobbins 22a and 22b (22c and 22d) are integrally molded with the resins 27 and 28 to prevent disconnection during vibration and shock during assembly, thereby providing two coils 20a and 20b. Since the positional relationship between 20c and 20d does not shift, output fluctuations between two systems due to position shift at the time of assembly are not generated. In addition, since the molded parts are integrally formed into one component by two detection units, positioning with the movable blocks 23A and 23B is facilitated, and the assembly time is short.

Moreover, by resin-molding in the state which correct | amended the deformation of the curved bobbin 22a, 22b (22c, 22d), the deformation of the curved bobbin 22a, 22b (22c, 22d) is correct | amended on the housing 25A, 25B side. There is no need to install a special member. In addition, if the two cores 60a, 60b, 60c, 60d are also resin-molded together, the positions are not shifted from each other, so that there is no variation in characteristics between the two systems due to positional shift during assembly.

(Embodiment 5)

The structure of the position sensor of this embodiment is the same as that of any one of Embodiment 1-4, the same code | symbol is attached | subjected to the same structure, and description is abbreviate | omitted. In this embodiment, the structure of the displacement signal Vout output from the signal processing circuit 40 is demonstrated.

If the ECU, which is a system that receives and processes the signal of the position sensor, is a digital circuit, if the displacement signal Vout is an analog signal, an error occurs by repeating an extra A / D conversion or D / A conversion, and accompanied by a response delay. However, if the displacement signal Vout is a digital signal, there is no such problem as an analog signal, and it is difficult to be affected by external noise during signal transmission. Thus, an example in which the displacement signal Vout output from the signal processing circuit 40 is constituted by a digital signal is shown. The signal processing circuit 40 includes a signal including an A / D conversion circuit (not shown) for converting the peak value V1 of the output voltage of the detector 50 into a digital signal, and a correction circuit for digital trimming the digital signal. A correction circuit (not shown) is provided.

FIG. 29 shows a first example of the displacement signal Vout output from the signal processing circuit 40, and the displacement signal Vout starts output having the width T1 of three pulse widths of the reference pulse Vr. Signal and a pulse signal which is output after a time T2 according to the positional information after the output start signal is output. On the ECU side, the relative position of the core 60 and the detection coil 20 can be determined by measuring the pulse width T1 of the output start signal and the time T2 until the pulse signal appears with a timer.

30 shows a second example of the displacement signal Vout output by the signal processing circuit 40, the displacement signal Vout being an output start signal having a width equal to three pulse widths of the reference pulse Vr, It consists of the number of pulse signals according to the positional information output following the output start signal. On the ECU side, the relative position of the core 60 and the detection coil 20 can be determined by counting the number of pulse signals following the output start signal with a counter.

FIG. 31 shows a third example of the displacement signal Vout output by the signal processing circuit 40, and the displacement signal Vout is composed of a pulse signal of duty ratio according to the positional information, and the duty ratio is on, The off time is determined by the number of pulses of the reference pulse Vr, respectively. On the ECU side, the relative position between the core 60 and the detection coil 20 can be determined by measuring the period and the pulse width with a timer.

Further, if the digital output of the required number of bits is secured, the number of wirings between the position sensors ECU increases, but according to the examples shown in Figs. 29 to 31, the signal lines are one. Moreover, the displacement signal Vout may be comprised with the pulse signal of the pulse width according to positional information. If the number of signal lines is not a problem, the displacement signal Vout may be composed of a digital signal having the number of bits satisfying the resolution required for position detection.

(Embodiment 6)

32 and 33 show cross-sectional structures and circuit configurations of the detection coil of the position sensor of the present embodiment, respectively. In consideration of using the position sensor of the present embodiment, the detection unit of the sensor is doubled based on the idea of the failsafe system.

The position sensor is configured to detect the detection coils 20e and 20f which are disposed to face the winding axial directions respectively wound on the hollow bobbins 15a and 15b, and the windings of the detection coils 20e and 20f are displaced in the bobbin direction X. The cores 60e penetrated into the hollows of the 15a and 15b, and the constant currents Ida and Idb which superimposed the alternating currents of a predetermined frequency and amplitude on the direct current of a predetermined amplitude, respectively, are provided to the detection coils 20e and 20f. The peak value of the voltage at both ends of the detection coil 20e determined by the constant current circuit 30A to be output, the constant current Ida output by the constant current circuit 30A, and the impedance Za of the detection coil 20e is determined. To the signal processing circuit 40a for converting the position information of the position 60e and the detection coil 20e into a displacement signal, the constant current Idb output by the constant current circuit 30A, and the impedance Zb of the detection coil 20f. The peak value of the voltage of both ends of the detection coil 20f determined by this indicates the positional information of the core 60e and the detection coil 20f. And a signal processing circuit (40b) for converting a signal above.

In the present embodiment, the two detection coils 20e and 20f share the same coil 60e mounted on the structural member (not shown), and the same constant current circuit 30A uses the constant currents Ida and Idb of a predetermined frequency and amplitude. ) Is output to the two detection coils 20e and 20f, respectively, so that the cost increase due to the duplication of the detection unit can be reduced.

In addition, if the active circuit portions of the constant current circuit 30A and the signal processing circuits 40a and 40b are constituted by monolithic ICs, the IC portion is the most expensive component, so that the cost increase due to the duplication of the detection portion can be further reduced. Can be.

Hereinafter, the specific usage of the position sensor of Embodiment 1 thru | or 6 is demonstrated. First, when used as an on-vehicle pedal detection position sensor, since the detection angle is narrow to about 30 °, curved bobbins having the same curvature can be arranged in the same plane, and the impedance of the detection coil can be complementary. Moreover, since it is arrange | positioned in a vehicle interior, the upper limit operation temperature is not so high. In addition, since there is a sufficiently large stroke with respect to the detection angle, it is possible to use a portion having a good linearity at the center of the stroke without devising much material or shape of the core.

Next, when used as a throttle position sensor, since the detection angle is larger than 90 ° and the mechanical stroke also needs to be large, two-stage overlapping of the curved bobbin shown in FIGS. 25 and 26 or FIG. 27. And a structure in which curved bobbins having different curvatures in the same angular range in the same plane is suitable as shown in FIG. 28. Moreover, since the margin of mechanical stroke with respect to a detection angle is limited, it is preferable to select a material from which the linearity of coil impedance, such as SUS430, is easy to be obtained as a core. Since the throttle position sensor is disposed in the engine room, a high operating upper limit temperature is required, and as a core, a material which is likely to obtain linearity is selected, and then a suitable bias current is applied to the coil, and the temperature characteristics due to angular displacement (temperature It is preferable to minimize the coefficient).

In addition, since the position sensor used for a plant, such as a power generation facility, becomes high temperature, iron chromium is used as a core material, an appropriate bias current is given to a coil, and temperature characteristics (temperature coefficient) by angular displacement are minimized. The method is preferred.

In addition, although the position sensor for angle detection used for a motorized bicycle uses only one detection part in terms of cost, in general, the position sensor for angle detection used for automobiles is a detection part in order to ensure reliability as a system. You may also plan to double.

As described above, the position sensor of the present invention includes a detection unit including a constant current circuit for outputting a constant current in which a predetermined current superimposes an alternating current of frequency and amplitude on a direct current of a predetermined amplitude, at least a detection coil for supplying a constant current, and a detection unit. A signal for outputting a displacement signal representing the positional information of the core and the detection coil based on the peak of the core of the magnetic material wound relative to the coil in the axial direction and the output voltage of the detection portion generated by the constant current. And a processing circuit, wherein a variation in the temperature coefficient of the peak value of the peak value of the output voltage of the detection section in the entire displacement section with respect to the detection coil of the core is determined by the impedance of the detection section at a predetermined frequency in the overall displacement section with respect to the detection coil of the core. The constant current of the direct current and alternating current so that it is smaller than the fluctuation range of the temperature coefficient of the alternating current component At least one of the temperature characteristic of the ratio, the ratio of the alternating current component and the direct current component of the impedance of the detection unit, the ratio of the direct current of the constant current to the alternating current, and the temperature characteristic of the ratio of the alternating current component and the direct current component of the impedance of the detecting unit To set it.

In this case, the detection coil can be freely selected in accordance with the detection target, and the displacement dependence of the temperature coefficient of the impedance of the detection coil can be easily reduced by setting a constant on the circuit, and the temperature coefficient of the impedance of the detection coil with respect to the displacement can be easily reduced. The change in can be compensated by a simple circuit.

It is preferable that the relative displacement core can be penetrated into the winding of the detection coil. In this case, the change in the impedance of the detection coil can be increased.

The temperature coefficient of the direct current component of the output voltage of the detection unit is the output voltage of the detection unit when the penetration amount of the core is larger than the temperature coefficient of the AC component of the output voltage of the detection unit when the penetration amount of the core to the winding of the detection coil is minimum. It is preferable to be close to the temperature coefficient of the alternating current component of. In this case, the fluctuation range of the temperature coefficient of the peak value of the output voltage of a detection part can be made small.

The constant current circuit includes an oscillation circuit for generating a voltage obtained by superimposing a DC voltage of a predetermined amplitude with an alternating voltage of a predetermined frequency and amplitude, and a voltage-current conversion circuit for converting an output voltage of the oscillating circuit into a current. It is preferable to set the ratio of the direct current of the constant current and the alternating current by setting the voltage and the alternating voltage, respectively. In this case, the ratio of the direct current of the constant current to the alternating current can be set by a simple circuit configuration and setting the constant on the circuit.

The constant current circuit includes an oscillation circuit for generating a voltage obtained by superimposing a DC voltage of a predetermined amplitude with an alternating voltage of a predetermined frequency and amplitude, and a voltage-current exchange circuit for converting an output voltage of the oscillating circuit into a current. You may set the temperature characteristic of the ratio of the direct current of direct current and alternating current by setting the temperature coefficient of the resistance value of the resistance which determines the value of the direct current voltage with which a circuit is equipped. Also in this case, the same effects as above can be obtained.

The constant current circuit includes an oscillation circuit for generating a voltage obtained by superimposing a DC voltage of a predetermined amplitude with an alternating voltage of a predetermined frequency and amplitude, and a voltage-current conversion circuit for converting an output voltage of the oscillating circuit into a current. It is preferable to set the temperature characteristic of the ratio of the alternating current component and the direct current component of the impedance of the detection unit by setting the temperature characteristic of the frequency of.

In this case, even when the constant current circuit is composed of an integrated circuit and the constant constant on the circuit cannot be easily set, a resistor or a capacitor for externally attaching a resistor or a capacitor for determining the oscillation frequency of the AC voltage is adopted. By selecting the temperature coefficient of, the temperature characteristic of the AC component of the detector impedance can be set.

The constant current circuit includes a direct current constant current circuit for outputting a direct current of a predetermined amplitude, and an alternating current constant current circuit for outputting an alternating current of a predetermined frequency and amplitude, the temperature characteristic of the amplitude of the direct current and the temperature of the frequency of the alternating current. By setting at least one of the characteristic and the temperature characteristic of the amplitude of the alternating current, the ratio of the direct current of the constant current to the alternating current, the ratio of the alternating current component to the direct current component of the impedance of the detector, and the ratio of the direct current to the alternating current of the constant current It is preferable to set any one or more of the temperature characteristic of and the temperature characteristic of the ratio of the alternating current component and the direct current component of the impedance of a detection part. In this case, the change in the temperature coefficient of the impedance of the detection coil with respect to the displacement can be compensated for by the simple circuit configuration and the setting of the constant on the circuit.

The detection unit includes a detection coil and a circuit element connected to the detection coil in series and whose impedance does not change due to the displacement of the core. The signal processing circuit includes a voltage of both ends of the detection circuit generated by the constant current and the series circuit of the circuit element. Outputting a displacement signal indicative of the position information of the core and the detection coil according to the peak value, and setting at least one of an AC component and a DC component of the impedance of the circuit element, and an AC component and a DC coefficient of the DC component of the impedance of the circuit element It is preferable to set at least one of the temperature characteristic of the ratio of the alternating current component and the direct current component of the impedance of the detector, and the ratio of the alternating current component and the direct current component of the impedance of the detector.

In this case, even when the constant current circuit is constituted by an integrated circuit and the constant on the circuit cannot be easily set, the change in the temperature coefficient of the detector impedance with respect to the displacement can be compensated by a simple circuit.

The circuit element is preferably a resistor. In this case, the impedance of the detector can be controlled at low cost.

The circuit element is preferably an inductor. In this case, the DC resistance and the AC impedance of the detector can be controlled at low cost.

The constant current circuit is composed of an integrated circuit having a resistor for setting the amplitude of the DC current, the frequency and the amplitude of the AC current, and a digital timing means for setting the value of the resistor, and by setting the value of the resistor by the digital trimming means, The temperature characteristic of the ratio of the direct current of the constant current and the alternating current, the ratio of the alternating current component and the direct current component of the impedance of the detection unit, the temperature characteristic of the ratio of the direct current of the constant current to the alternating current, and the temperature of the ratio of the impedance alternating current component and the direct current component of the detection unit It is preferable to set any one or more of the characteristics. In this case, the change in the temperature coefficient of the impedance of the detection coil with respect to the displacement can be easily compensated by a simple circuit.

The signal processing circuit preferably includes a rectifier circuit and a circuit for peak holding the output of the rectifier circuit. In this case, the signal processing circuit can be constituted by a simple circuit.

The signal processing circuit preferably includes an amplifier having a temperature coefficient of reverse polarity with the temperature coefficient of the peak value of the output voltage of the detector, and outputs a displacement signal indicating the position information of the core and the detection coil in accordance with the output of the amplifier. . In this case, the output of the amplifier is a signal that depends only on the temperature compensated displacement, and by processing this output a temperature compensated displacement signal can be obtained.

The AC voltage generated by the oscillation circuit is preferably a triangle wave. In this case, the AC voltage can be obtained from the oscillation circuit more simply than the sinusoidal voltage.

The AC current output by the AC constant current circuit is preferably a triangular wave. In this case, the AC voltage can be obtained from the AC constant current circuit more simply than the sinusoidal voltage.

The number of winding turns of the detection coil, the winding pitch of the winding, and the frequency of the signal input to the detection coil are the temperature coefficient of the impedance component of the detection coil's winding and the impedance of the detection coil due to the relative displacement of the core with respect to the detection coil. It is preferable that it is each value to which the temperature coefficient of a component becomes the same. In this case, the impedance of the detection coil when the core is not penetrated can be controlled so that the change in temperature of the impedance does not change due to the relative displacement of the core and the detection coil.

The core may be formed of a material in which the temperature coefficient of the impedance component of the winding of the detection coil is equal to the temperature coefficient of the impedance component of the detection coil due to the relative displacement of the core to the detection coil. Also in this case, the same effect as above can be obtained.

The surface treatment applied to the core may be a surface treatment in which the temperature coefficient of the impedance component of the winding of the detection coil is equal to the temperature coefficient of the impedance component of the detection coil due to the relative displacement of the core to the detection coil. Also in this case, the same effect as above can be obtained.

The core preferably forms at least the surface of a material having a small temperature coefficient of volume resistivity. In this case, the temperature variation of the impedance of the detection coil when the core is inserted can be reduced.

The core preferably forms at least a surface of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and manganine. In this case, at least the surface of the core can be easily formed of a material having a small temperature coefficient of volume resistivity.

The core is preferably formed by bending a heating wire cut to a desired length. In this case, the temperature variation of the impedance of the detection coil when the core is inserted can be made smaller, and the loss of material can be reduced.

The heating wire is preferably formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and manganine. In this case, the heating wire cut to the desired length can be easily formed by bending.

The winding of the detection coil is preferably formed of any one of nichrome, manganine and a copper-nickel alloy. In this case, it is possible to reduce the temperature variation of the impedance of the detection coil when the core is inserted.

It is preferable that the magnetic flux passes through the predetermined length portion from the end of the core more than the other portion. In this case, the end effect is reduced, and the section | piece which can ensure output linearity can be enlarged.

It is preferable that the predetermined length portion from the end of the core is thicker than the other portion. In this case, it is advantageous when the core is molded by metal injection molding, or the core can be easily formed by a combination of two members.

The predetermined length portion from the end of the core is preferably formed of a material having a higher permeability than the other portion. In this case, since the thickness of the core can be made constant, it is mechanically stable and the core can be easily formed even by a combination of two members.

The portion of the predetermined length from the end of the core is preferably surface treated with a material having a higher permeability than the other portion. In this case, since the thickness of a core can be made constant, even if it is dynamically stable and a curved core can be formed easily.

It is preferable that a core consists of electron stainless steel which permalloy plated the surface of the part of predetermined length from an edge part. In this case, the balance of the magnetic permeability of the end part of a core and another part is good, and is excellent also in corrosion resistance.

It is preferable that the end of the core is chamfered to remove the edge. In this case, the core is not caught inside the bobbin, and deterioration of linearity due to the latch can be prevented.

The detection coil preferably has a shape that is curved at a predetermined curvature and has a housing having a means for fixing the detection coil and correcting a change in curvature of the detection coil. In this case, the change in curvature of the detection coil can be corrected and prevented.

The housing preferably contacts the at least a portion of the inner radial portion of the detection coil to correct for the change in curvature of the detection coil. In this case, the change in the curvature of the detection coil can be reliably corrected and prevented.

The position sensor includes a bobbin wound around a detection coil, and it is preferable to resin mold the coil and the bobbin before assembly. In this case, it is possible to prevent disconnection at the time of assembling and to prevent disconnection against vibration and impact, and in the case of the curved bobbin, the curvature of the detection coil on the housing side by resin molding in the state where deformation is corrected. Even if there is no means for correcting the change, the change in the curvature of the detection coil can be corrected and prevented.

The position sensor is provided with two bobbins each wound with a detection coil, and it is preferable that the two detection coils and the two bobbins are resin-molded integrally before assembly. In this case, in addition to the above effects, the positional relationship between the two detection coils does not deviate, and output fluctuations between the two systems of detection due to the positional shift during assembly do not occur.

It is preferable that the position sensor is provided with two detection coils and two cores, and resin molds integrally the two cores which respectively penetrate into two detection coils. Also in this case, the same effect as above can be obtained.

The detection coil has two detection coils curved at the same curvature, and the cores are infiltrated into the two detection coils by rotating about the rotation axis, respectively, and have two cores curved at the same curvature, and the two detection coils It is preferable to arrange | position in the rotation axis direction of a core.

In this case, since the expected angle of the winding portion of the detection coil and the mechanical rotation angle of the movable block can be increased, the range of the rotation angle with good linearity of the impedance of the detection coil can be expanded. In addition, since the means of the two detection coils can be made the same, the characteristics of the two detection coils can be made the same, which is advantageous in terms of coil processing and cost.

The detection coil has two detection coils curved at different curvatures, and the cores are infiltrated into the two detection coils by rotating about a rotation axis, respectively, and have two cores curved at different curvatures. The coil is preferably arranged on the same rotational angle and on the same plane with respect to the axis of rotation of the core.

In this case, since the expected angle of the winding portion of the detection coil and the mechanical rotation angle of the movable block can be increased, the range of the rotation angle where the linearity of the impedance of the detection coil is good can be extended and the thickness can be reduced.

The signal processing circuit includes a signal correction circuit having an A / D conversion circuit for converting a peak value of the output voltage of the detector into a digital signal, and a correction circuit for digitally trimming the digital signal, and the displacement signal output by the signal processing circuit. Is preferably a digital signal of the number of bits that satisfies the resolution required for position detection.

In this case, if the system (e.g., ECU) for which the output of the position sensor is inputted and processed is a digital circuit, an error occurs by repeating useless AD conversion and DA conversion if the output of the position sensor is an analog signal. Although accompanied by a response delay, this problem does not occur because the output of the position sensor is a digital output. In addition, compared to analog outputs, the signal transmission is not affected by external noise. In addition, since the digital signal is the number of bits that satisfies the required resolution, the ECU side can read in real time and perform the processing quickly.

The signal processing circuit includes a signal correction circuit having an A / D conversion circuit for converting a peak value of the output voltage of the detector into a digital signal, and a correction circuit for digitally trimming the digital signal, and the displacement signal output by the signal processing circuit. Is preferably composed of an output start signal and a pulse signal output over time after the output start signal is output.

In this case, if the system (e.g., ECU) for which the output of the position sensor is inputted and processed is a digital circuit, if the output of the position sensor is an analog signal, an error occurs by repeating useless AD conversion and DA conversion. Although accompanied by a response delay, this problem does not occur since the output of the position sensor is a digital output. In addition, compared to the analog output, the signal lines are not affected by external noise and the signal lines can be reduced to one.

The signal processing circuit includes a signal correction circuit including an A / D conversion circuit for converting a peak value of the output voltage of the detector into a digital signal, and a correction circuit for digitally trimming the digital signal, and the displacement signal output by the signal processing circuit. May be composed of an output start signal and a pulse signal having a duty ratio corresponding to positional information that is continuously output to the output start signal. Also in this case, the same effect as above can be obtained.

The signal processing circuit includes a signal correction circuit having an A / D conversion circuit for converting a peak value of the output voltage of the detector into a digital signal, and a correction circuit for digitally trimming the digital signal, and the displacement signal output by the signal processing circuit. May be composed of an output start signal and a pulse signal having a pulse width corresponding to the positional information continuously outputted to the output start signal. Also in this case, the same effect as above can be obtained.

The signal processing circuit includes a signal correction circuit having an A / D conversion circuit for converting a peak value of the output voltage of the detector into a digital signal, and a correction circuit for digitally trimming the digital signal, and the displacement signal output by the signal processing circuit. May be composed of an output start signal and a number of pulse signals corresponding to positional information that is continuously output to the output start signal. Also in this case, the same effect as above can be obtained.

It is preferable that two detection coils are provided and two detection coils share the same core attached to the structural member. In this case, it is possible to reduce the increase in cost caused by the duplication of the detection unit.

It is preferable to provide two detection coils, and the same constant current outputs the electrostatic amount of predetermined frequency and amplitude to two detection coils. In this case as well, it is possible to reduce the increase in cost caused by the duplication of the detection unit.

The active circuit of each of the above circuits is preferably composed of a monolithic IC. In this case, an increase in the cost due to the duplication of the detection unit can be reduced. In particular, since the IC unit is the most expensive component, the merit of common use is large.

As mentioned above, according to this invention, the position sensor which can compensate the change of the temperature coefficient of the impedance of a detection coil with respect to a displacement with a simple circuit can be provided, and it is possible to provide the It can use suitably for the position sensor used for a plant, the position sensor for angle detection used for bicycles with a motor, etc.

Claims (44)

A constant current circuit for outputting a constant current superimposed on a direct current of a predetermined amplitude and an alternating current of a predetermined frequency and amplitude; A detector comprising at least a detection coil to which the constant current is supplied; A core made of a magnetic material relatively displaced in the crimping direction of the detection coil with respect to the detection coil; And A signal processing circuit for outputting a displacement signal representing position information of the core and the detection coil in accordance with a peak value of an output voltage of the detection unit generated by the constant current; The fluctuation range of the temperature coefficient of the peak value of the peak value of the output voltage of the detector in the entire displacement section of the core of the core is alternating with the detector impedance at the predetermined frequency in the entire displacement section of the core of the core. The ratio of the direct current and the alternating current of the constant current, the ratio of the alternating current component and the direct current component of the impedance of the detection unit, and the temperature characteristics of the ratio of the direct current and alternating current of the constant current so as to be smaller than the fluctuation range of the temperature coefficient of the component And setting at least one of temperature characteristics of the ratio of the alternating current component and the direct current component of the impedance of the detection unit. 2. The position sensor according to claim 1, wherein said core is free to penetrate into a winding of said detection coil. 2. The temperature coefficient of the direct current component of the output voltage of the detection section is characterized in that the penetration amount of the core is larger than the temperature coefficient of the AC component of the output voltage of the detection section when the penetration amount of the core to the winding of the detection coil is minimum. A position sensor, which is close to a temperature coefficient of an alternating current component of an output voltage of the detection section at the maximum. The oscillator according to claim 1, wherein the constant current circuit includes an oscillation circuit for generating a voltage obtained by superimposing a DC voltage of a predetermined amplitude with an alternating voltage of a predetermined frequency and amplitude, and a voltage-current for converting an output voltage of the oscillating circuit into a current. With a conversion circuit, And setting a ratio of the DC current and the AC current of the constant current by setting the DC voltage and the AC voltage, respectively. The oscillator according to claim 1, wherein the constant current circuit includes an oscillation circuit for generating a voltage obtained by superimposing a DC voltage of a predetermined amplitude with an alternating voltage of a predetermined frequency and amplitude, and a voltage-current for converting an output voltage of the oscillating circuit into a current. With a conversion circuit, And a temperature characteristic of the ratio of the direct current of the constant current to the alternating current by setting the temperature coefficient of the resistance value of the resistor for determining the value of the direct current voltage included in the oscillation circuit. The oscillator according to claim 1, wherein the constant current circuit includes an oscillation circuit for generating a voltage obtained by superimposing a DC voltage of a predetermined amplitude with an alternating voltage of a predetermined frequency and amplitude, and a voltage-current for converting an output voltage of the oscillating circuit into a current. With a conversion circuit, The temperature sensor of the ratio of the alternating current component and the direct current component of the impedance of the said detection part is set by setting the temperature characteristic of the frequency of the said alternating voltage. 2. The constant current circuit according to claim 1, wherein the constant current circuit includes a direct current constant current circuit for outputting a direct current having a predetermined amplitude, and an alternating current constant current circuit for outputting an alternating current having a predetermined frequency and amplitude, By setting at least one of the temperature characteristic of the amplitude of the direct current, the temperature characteristic of the frequency of the alternating current, and the temperature characteristic of the amplitude of the alternating current, the ratio of the direct current and alternating current of the constant current and the detection unit At least one of a temperature characteristic of the ratio of the impedance alternating current component and the direct current component, the ratio of the direct current of the constant current to the alternating current, and the temperature characteristic of the ratio of the alternating current component to the direct current component of the impedance of the detection unit Position sensor. The said detection part is provided with the said detection coil and the circuit element connected in series with the said detection coil, and the impedance which does not change an impedance by the displacement of the said core, The signal processing circuit outputs a displacement signal indicating the positional information of the core and the detection coil in accordance with the peak value of the voltage between both ends of the detection circuit and the series circuit of the circuit element generated by the constant current, By setting at least one of an AC component and a DC component of the impedance of the circuit element, and a temperature coefficient of the AC component and the DC component of the impedance of the circuit element, the ratio of the impedance AC component and the DC component of the detection unit to the And at least one of temperature characteristics of the ratio of the AC component of the impedance to the DC component of the impedance. 9. The position sensor of claim 8, wherein the circuit element is a resistor. 9. The position sensor of claim 8, wherein the circuit element is an inductor. The constant current circuit of claim 1, wherein the constant current circuit comprises an integrated circuit including a resistor for setting the amplitude of the DC current, the frequency and the amplitude of the AC current, and digital trimming means for setting the value of the resistance, By setting the value of the resistance by the digital trimming means, the ratio of the direct current of the constant current to the alternating current, the ratio of the alternating current component to the direct current component of the impedance of the detection unit, and the ratio of the direct current of the constant current to the alternating current And at least one of a temperature characteristic of and a temperature characteristic of a ratio of an alternating current component and a direct current component of the impedance of the detection unit. The position sensor according to claim 1, wherein the signal processing circuit includes a rectifying circuit and a circuit for peak holding the output of the rectifying circuit. 2. The signal processing circuit according to claim 1, wherein the signal processing circuit includes an amplifier having a temperature coefficient of reverse polarity with a temperature coefficient of a peak value of an output voltage of the detection unit, and the position of the core and the detection coil according to the output of the amplifier. And a displacement sensor for outputting information. The position sensor according to claim 4, wherein the AC voltage generated by the oscillation circuit is a triangular wave. 8. The position sensor according to claim 7, wherein the alternating current output from the alternating current constant current circuit is a triangular wave. The method of claim 1, wherein the number of winding turns of the detection coil, the winding pitch of the windings, and the frequency of the signal input to the detection coil are determined by a temperature coefficient of an impedance component of the winding of the detection coil and the core of the detection coil. And each value at which the temperature coefficient of the impedance component of the detection coil due to relative displacement with respect to is equal to each other. The method of claim 1, wherein the core is made of a material in which the temperature coefficient of the impedance component of the winding of the detection coil is equal to the temperature coefficient of the impedance component of the detection coil due to the relative displacement of the core to the detection coil. Position sensor, characterized in that formed. 2. The surface treatment of the core according to claim 1, wherein the surface treatment of the core comprises: a temperature coefficient of an impedance component of a winding of the detection coil and a temperature coefficient of an impedance component of the detection coil due to the relative displacement of the core to the detection coil. The surface sensor which becomes surface treatment to become the same. The position sensor according to claim 1, wherein the core is formed of a material having at least a surface having a small temperature coefficient of volume resistivity. 20. The position sensor of claim 19, wherein the core is formed of at least one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and manganese. The position sensor according to claim 19, wherein the core is formed by bending a heating wire cut to a desired length. 22. The position sensor according to claim 21, wherein the heating wire is formed of any one of a nickel-chromium alloy, a nickel-chromium-iron alloy, an iron-chromium-aluminum alloy, a copper-nickel alloy, and manganine. The position sensor of claim 1, wherein the winding of the detection coil is formed of any one of chromium, manganese, and copper-nickel alloy. The position sensor according to claim 1, wherein a predetermined length portion from an end of the core is more likely to allow magnetic flux to pass than other portions. The position sensor according to claim 24, wherein a predetermined length portion from the end of the core is thicker than the other portion. 25. The position sensor of claim 24, wherein a predetermined length portion from the end of the core is formed of a material having a higher permeability than the other portion. A position sensor according to claim 24, wherein the predetermined length portion from the end of the core is surface treated with a material having a higher transmittance than the other portion. 28. The position sensor according to claim 27, wherein the core is made of electronic stainless steel, which has undergone permloy plating on a surface of a predetermined length portion from an end portion. The position sensor according to claim 1, wherein the end of the core is chamfered to remove an edge. The position sensor according to claim 1, wherein the detection coil has a curved shape with a predetermined curvature and has a housing for fixing the detection coil to correct a change in curvature of the detection coil. . 31. The position sensor of claim 30, wherein the housing corrects a change in curvature of the detection coil by contacting at least a portion of an inner radius portion of the detection coil. The position sensor according to claim 1, further comprising a bobbin wound around the detection coil, and wherein the coil and the bobbin are resin molded before assembly. The position sensor according to claim 1, further comprising two bobbins each wound around the detection coil, and wherein the two detection coils and the two bobbins are integrally resin-molded before assembly. The position sensor according to claim 1, wherein each of the two detection coils and the cores is provided, and the two cores respectively inserted into the two detection coils are integrally resin-molded. The method of claim 1, wherein the detection coil has two detection coils curved at the same curvature, The cores are infiltrated into the two detection coils by rotating about a rotation axis, respectively, and have two cores curved at the same curvature, The two detection coils are arranged in the direction of the axis of rotation of the core superimposed. The method of claim 1, wherein the detection coil has two detection coils curved at different curvatures, The core is provided with two cores which are respectively penetrated into the two detection coils by rotating about a rotation axis, and are curved at different curvatures, The two detection coils are arranged on the same rotational angle and on the same plane with respect to the axis of rotation of the core. 2. The signal processing circuit according to claim 1, wherein the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection unit into a digital signal, and a signal correction circuit including a correction circuit for digitally trimming the digital signal. , And the displacement signal output by the signal processing circuit is a digital signal of the number of bits satisfying the resolution required for position detection. 2. The signal processing circuit according to claim 1, wherein the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection unit into a digital signal, and a signal correction circuit including a correction circuit for digitally trimming the digital signal. , And the displacement signal output by the signal processing circuit comprises an output start signal and a pulse signal that is output over time according to the position information after the output start signal is output. 2. The signal processing circuit according to claim 1, wherein the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection unit into a digital signal, and a signal correction circuit including a correction circuit for digitally trimming the digital signal. , And the displacement signal output by the signal processing circuit is composed of an output start signal and a pulse signal having a duty ratio according to the position information continuously outputted to the output start signal. 2. The signal processing circuit according to claim 1, wherein the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection unit into a digital signal, and a signal correction circuit including a correction circuit for digitally trimming the digital signal. , And the displacement signal output by the signal processing circuit is composed of an output start signal and a pulse signal having a pulse width in accordance with the position information continuously output to the output start signal. 2. The signal processing circuit according to claim 1, wherein the signal processing circuit includes an A / D conversion circuit for converting a peak value of an output voltage of the detection unit into a digital signal, and a signal correction circuit including a correction circuit for digitally trimming the digital signal. , And the displacement signal output by the signal processing circuit is composed of an output start signal and a pulse signal of a number corresponding to the position information output continuously to the output start signal. The position sensor according to claim 1, further comprising two detection coils, wherein the two detection coils share the same core attached to the structural member. The position sensor according to claim 1, further comprising two detection coils, wherein the same constant current circuit outputs a constant current of a predetermined frequency and amplitude to the two detection coils. 44. The position sensor according to claim 43, wherein the active circuit of each circuit is composed of a monolithic IC.